1. Field of the Invention
The present invention relates to a method for manufacturing a diffuser for a backlight module and, more particularly, to a method for manufacturing a diffuser using particles as a mask.
2. Description of Related Art
Currently, flat panel displays, such as LCDs and PDPs are gradually replacing the traditional CRT displays and becoming the main stream of displays due to their light weight and thin size.
Contemporary flat panel displays use backlight modules as their sources of light. Generally, a backlight module includes a light source, a light guide, and two diffusers. The diffusers are used to make a uniform dispersion of light and prevent the displaying zone of a display from suffering non-uniform illumination.
The common methods for manufacturing a diffuser include the particle adhesion method and the sandblast method. In the particle adhesion method, the scattering particles are adhered on the surface of a transparent substrate by using an adhesive, as shown in FIG. 1, so that the light is scattered by the particles and becomes uniform. The sandblast method firstly forms a non-uniform surface on the transparent substrate by sand grinding. The light from the light source is scattered by the non-uniform surface to harmonize the light. The disadvantages of the particle adhesion method lie in that the scattering particles cannot be dispersed uniformly in the adhesive due to the gravity or static electricity factors, and the sieving of particle size of the scattering particles is complex and needs to be done carefully because it will affect the performance of light diffusion. Besides, those scattering particles are mostly made of hard inorganic materials, such as silica or calcium carbonate, which will damage the surface of a liquid crystal (LC) cell through direct contact and therefore a passivation layer is further needed.
The Japanese patent JP5173130 disclosed a light guide having functions of diffusion, reflection, and total reflection, wherein the function of diffusion is achieved through roughening the surface of the light guide by using the sandblast method. However, the sandblast method cannot precisely control the roughness of the surface and the uniformity thereof so that the quality of light guide is not easily controlled in mass production.
Therefore, it is desirable to provide a method for manufacturing a diffuser for a backlight module to mitigate and/or obviate the aforementioned problems.